At 8:30 p.m. last Friday, Mark Andrew Gravel was watching nervously as 40-odd assembled diners in the exposed brick basement of the Wythe Hotel in Williamsburg, Brooklyn plunged their forks into a plate of food he had just served.

This plate was piled with a curious combination of sunchoke (known to some as Jerusalem artichoke), olive, cattail heart, buttermilk, and whey.

In a different era or a less rarefied location, such a plate might suggest poverty — someone forced to scrounge for scraps (whey) and weeds (cattails) because they couldn't afford anything else. But here in Brooklyn, at a Food Book Fair event, it was part of a $150 meal, and the customers expected it to taste good.

It was the buttermilk whey sauce that worried Gravel. "I was afraid it was going to curdle," he said.

Chefs Leif Hedendal and Mark Andrew Gravel received this toothwort root and knotweed in the mail from New England forager Evan Strusinski.

Still, Gravel later admitted, the buttermilk was hardly the most risky undertaking. Gravel and his co-collaborator, Leif Hedendal, a San Francisco-based chef-artist, had agreed to assemble eight courses of food with several ingredients they had never heard of before, much less tasted or cooked with.

"We were doing some serious improvisational cooking," Gravel, a chef and designer, told The Salt.

The new generation of chefs deeply committed to seasonal, wild and local foods have to be flexible, because they often aren't sure how or what they're going to cook until the last minute.

For this dinner, Gravel and Hedendal worked with professional forager Evan Strusinski, a purveyor of wild foods from the Northeast.

They pored over Strusinski's order form, gamely selecting lily shoots, tamarack shoots, cattails, ground ivy, toothwort root, and sweetflag, along with more familiar wild vittles like ramps. A couple of days before the dinner, boxes full of foraged food from Vermont arrived in the mail.

"Almost every single [ingredient] we got from Evan was new to me," said Hedendal. "So it was pretty exciting."

Exciting, but also daunting: Hedendal and Gravel were cooking for people who'd paid a lot of money to eat food that might also be called weeds.

Hedendel and Gravel had been expecting a bunch of wild mushrooms, which, due to this winter's warm weather, did not materialize. But as seasonal cooks know well, there's no point in lamenting what you don't have. You just need to move on.

So they did, to fresh East Coast oysters and blue crab they found at a local fish market and an assortment of greens grown at the Brooklyn Grange, an urban rooftop farm a few miles from Williamsburg.

Then they tackled the boxes in the fridge, using the Internet and their intuition to figure out how to cook their obscure woodland finds.

"You taste it and feel it to get a sense of texture, and try to go with your gut," said Gravel. As for the cattails, Gravel turned to a trusted friend: Butter. "I sliced them and cooked them down in butter, like leeks. Then I put them in acast iron skillet and crisped them up to get a light, crunchy texture."

Upon receiving a plate of sunchoke, cattail and whey, one diner poked at the sunchoke, turning it this way and that on her fork. "I've never been able to make sunchokes taste this good," she observed.

"It's all about the oil," said her tablemate, Taylor Erkkinen, co-owner of The Brooklyn Kitchen, a kitchenware store that offers cooking classes. "See how it has been totally roasted in oil?"

As we've reported before, there's good reason for amateur chefs and foragers to make use of these foods that sprout around us, even along city streets. They're nutritious, and even better, they're free — just as long as you don't pick something poisonous and land in the hospital.